1. Field of the Invention
The present invention relates to a vibration damping device including: a first mounting member fixable to a first component for vibration damped connection; a second mounting member fixable to another component; and a main rubber elastic body elastically connecting the first and second mounting members. More specifically, the present invention is concerned with a vibration damping device with a rubber heat-insulating cover, which is novel in structure having a rebound stopper mechanism for limiting in a cushion-wise fashion an amount of displacement of the first mounting member and the second mounting member in the direction of mutual separation, as well as a rubber heat-insulating cover for protecting the main rubber elastic body from the effects of heat.
2. Description of the Related Art
Among vibration damping devices such as vibration damping connections and vibration damping supports adapted for interposition between components that make up a vibration transmission system, one type of device proposed in the past has a structure which includes a first mounting member fixable to a component intended for vibration damped connection, and a second mounting member fixable to another component, which members are elastically connected by a main rubber elastic body. Application of vibration damping devices having this structure as automotive engine mounts, body mounts, or suspension bushings for example, is the subject of ongoing research.
In order to exhibit good vibration isolating action, a vibration damping device is desired to have sufficiently soft spring characteristics. On the other hand, upon input of large vibrational load, the vibration damping device is required to prevent large displacement of one component and the other component which are connected in a vibration damping fashion. Consequently, in vibration damping devices, the first mounting member and the second mounting member are provided typically with a stopper mechanism designed to limit the amount of their relative displacement.
JP-A-2005-172202 and JP-A-2004-276764 disclose one example of such stopper mechanisms in the form of a rebound type stopper mechanism that includes an arched stopper member fastened at both of its leg sections to the second mounting member so as to straddle the first mounting member in the axis-perpendicular direction, with the center section of the stopper member positioned in opposition in the axial direction to the first mounting member and a cushioning rubber disposed on the face of the center section of the stopper member in opposition to the first mounting member. With this design, in the event that the first mounting member and the second mounting member experience appreciable displacement in the direction of mutual separation (rebound direction) due to input of a large load, the amount of displacement of the first and second mounting members in the rebound direction will be limited by the stopper striking the first mounting member via the cushioning rubber.
However, where the cushioning rubber disposed on the stopper member, if the cushioning rubber and the center section of the stopper member are integrally molded by vulcanization as taught in JP-A-2005-172202, it will be necessary to provide a special mold for vulcanization molding that corresponds in design to the size and shape of the stopper member, or in the event of any design modification of the stopper member to modify the design of the mold in association therewith. This results in a more complicated production process as well as limiting the degree of freedom in design of the cushioning rubber. Thus, this was not always an effective approach for disposing the cushioning rubber on the stopper member. It would also be possible, for example, to form the cushioning rubber as a separate component from the stopper member and to then secure it to the stopper position of the stopper member. However, this would require a laborious positioning and fastening operation, and in some instances it was difficult to achieve sufficient stability of fastening of the cushioning rubber.
Moreover, vibration damping devices furnished with a stopper mechanism of the sort described above are frequently employed in automotive engine mounts or other systems where they are exposed to input of large-amplitude vibration for example. A resultant problem is that if the main rubber elastic body is exposed directly to radiant heat or exhaust gases from an engine, its durability may decline to the point that it becomes difficult to obtain sufficient vibration damping action based on resilience of the main rubber elastic body.
One known measure for addressing this problem is a heat-insulating cover-equipped vibration damping device having a heat-insulating cover (heat-insulating panel) disposed spacedly covering the outside surface of the main rubber elastic body so as to reduce the effects of outside heat on the main rubber elastic body. Such a device is taught in JP-A-2004-276764, for example.
With the heat-insulating cover-equipped vibration damping device according to JP-A-2004-276764, the first mounting member is fastened to a mounting member on the power unit side, the cushioning rubber of the stopper member is disposed so as to strike the first mounting member via the mounting member on the power unit side, and the center section of the rubber heat-insulating cover is supported on the first mounting member. For this reason, within the limited space available to the inside of the arched stopper member, it was necessary to ensure a site for supporting the heat-insulating cover region, in addition to ensuring a site for fastening of the mounting member on the power unit side, but it was sometimes difficult to ensure sufficient room for both. Additionally, since a cushioning rubber with a separate structure must be affixed to the stopper member, a larger number of assembly steps were required, making it difficult to achieve improved production efficiency.